Squamous epithelial cell carcinoma antigen is a tumor marker for squamous carcinoma, and it is a glycoprotein. In 95% of healthy controls, its normal value is less than 1.5 ng/mL. serum levels of squamous epithelial cell carcinoma antigen are elevated in some pathological types of non-small cell lung cancer and also in liver and kidney dysfunction, but smoking does not affect its serum concentration. 35% of patients with squamous carcinoma have elevated squamous epithelial cell carcinoma antigen serum concentrations, while only 17% of patients with non-squamous carcinoma are elevated. The level of squamous epithelial cell carcinoma antigen correlates with tumor load and tumor cell activity, and continuous dynamic monitoring is useful to monitor the efficacy of treatment, especially surgery. The biological half-life of squamous epithelial cell carcinoma antigen in blood is only a few minutes, and once a radical tumor is removed, the preoperative abnormal squamous epithelial cell carcinoma antigen can rapidly decrease to normal within 72 hours; while after palliative resection, squamous epithelial cell carcinoma antigen levels can temporarily decrease, but most of them are still higher than normal. Squamous epithelial cell carcinoma antigen can be used as an important reference indicator for post-treatment follow-up.